Project Summary: Candidate?The following application is intended to initiate the research career of Kristi J. Warren, PhD within the VA Nebraska Western Iowa Health Care System under the mentorship of [Robert Paine III, MD; a well-respected, VA-funded pulmonary researcher and clinician for the past 20+ years]. Dr. Warren received her PhD in Immunobiology in 2012 and has since completed her postdoctoral training focused exclusively in the pulmonary immunologic sciences. Environment?[The University of Utah is adjacent to the George E. Wahlen VA Medical Center and research hospital where clinical and scientific relationships have been established to complete the proposed studies.] The research environment is collegial and supportive with a multitude of opportunities for interaction with other scientists with similar interests. Specifically, Dr. Warren will have every opportunity to discuss/present her work for crucial feedback and direction from senior VA researchers. Research?In recent years, asthma and other chronic respiratory illnesses are increasingly diagnosed in the Veteran population. There is a sex-based disparity in asthma such that severe asthma is more prevalent in adult female Veterans than males, and more asthma-linked deaths occur in women than men. In general, ovarian hormones are thought to contribute to disease exacerbation, whereas testosterone protects against asthma. Recently, attention was drawn to the group 2 innate lymphoid cells (ILC2), which are shown to produce large amounts of asthma-promoting cytokines (IL-5 and IL-13) following allergen exposure. We observed a sex difference in activated ILC2 such that lung ILC2 isolated from female allergen-treated mice produced higher IL-5, IL-13, and the type 2 chemokines, CCL17 and CCL22, in comparison to males. In this research proposal we will use gonadectomized female mice treated with slow-release hormone pellets to evaluate the independent effect of estrogen, progesterone, and [testosterone] in experimental asthma. There are two goals for Aim 1: (1) define sex differences in recruitment and localization of ILC2 in the lung mediated through the chemokine receptors CCR4 and CRTH2 and their cognate chemokines, CCL17/22 and PGD2, respectively (subaim 1a). (2) Subaim 1b will define the chemokine expression specifically by activated lung-ILC2 following allergen exposure. Because ILC2 are in close proximity to the airway epithelium and other resident immune cells, these studies are designed to separate the sex hormone effect on the total chemokine milieu of the lung from that of the activated ILC2. These studies will comprehensively define the sex hormone-based effects on the chemokine milieu developed in the lung during allergen challenge. Aim 2 will investigate sex differences in IL-33-mediated activation of ILC2, which drives the production of IL-5 and IL-13 through a MyD88- dependent signaling pathway. IL-33-MyD88 signaling has not been previously evaluated in ILC2, nor has the effect of sex hormones on IL-33 signaling been established. In subaim 2a we will examine the mechanism by which sex hormones alter IL-33-induced activation of ILC2 in mice, and in subaim 2b we will isolate ILC2 from the blood of healthy and asthmatic, female and male Veteran donors to translate our findings to Veteran population. Aim 3 will similarly examine male and female ?C-dependent signaling mechanisms in mouse and human ILC2. Our preliminary data from human ILC2 suggests that female ILC2 proliferate more efficiently than male ILC2 when stimulated with IL-2 and IL-7, ?C-dependent cytokines. Because ?C is required for ILC2 survival and proliferation, we will evaluate JAK-STAT and PI3K-TOR activation for interactions with the sex hormones following IL-2 and IL-7 stimulation. The scope of this project is such that novel signaling mechanisms can be defined, leading to personalized therapeutic strategies designed to more effectively limit the asthma burden in the highly susceptible Veteran population. Furthermore, this project will effectively launch the independent scientific career of the candidate within the VA medical-research community.